一.dns服务
1.解决的问题
为了通过服务的名字在集群内进行服务相互访问,需要创建一个dns服务
2.k8s中使用的虚拟dns服务是skydns
二.搭建
1.创建并应用skydns-rc.yaml
[root@master dns]# cat skydns-rc.yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: kube-dns
namespace: kube-system
labels:
k8s-app: kube-dns
kubernetes.io/cluster-service: "true"
spec:
#指定副本数
replicas: 1
# replicas: not specified here:
# 1. In order to make Addon Manager do not reconcile this replicas parameter.
# 2. Default is 1.
# 3. Will be tuned in real time if DNS horizontal auto-scaling is turned on.
strategy:
rollingUpdate:
maxSurge: 10%
maxUnavailable: 0
selector:
matchLabels:
k8s-app: kube-dns
template:
metadata:
labels:
k8s-app: kube-dns
annotations:
scheduler.alpha.kubernetes.io/critical-pod: ''
scheduler.alpha.kubernetes.io/tolerations: '[{"key":"CriticalAddonsOnly", "operator":"Exists"}]'
spec:
containers:
- name: kubedns
image: docker.io/ist0ne/kubedns-amd64:latest
resources:
# TODO: Set memory limits when we've profiled the container for large
# clusters, then set request = limit to keep this container in
# guaranteed class. Currently, this container falls into the
# "burstable" category so the kubelet doesn't backoff from restarting it.
limits:
memory: 170Mi
requests:
cpu: 100m
memory: 70Mi
livenessProbe:
httpGet:
path: /healthz-kubedns
port: 8080
scheme: HTTP
initialDelaySeconds: 60
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 5
readinessProbe:
httpGet:
path: /readiness
port: 8081
scheme: HTTP
# we poll on pod startup for the Kubernetes master service and
# only setup the /readiness HTTP server once that's available.
initialDelaySeconds: 3
timeoutSeconds: 5
args:
#指定一级域名
- --domain=rorshach.com.
- --dns-port=10053
- --config-map=kube-dns
#增加kube-master-url,指向k8s_master地址
- --kube-master-url=http://192.168.2.17:8080
# This should be set to v=2 only after the new image (cut from 1.5) has
# been released, otherwise we will flood the logs.
- --v=0
env:
- name: PROMETHEUS_PORT
value: "10055"
ports:
- containerPort: 10053
name: dns-local
protocol: UDP
- containerPort: 10053
name: dns-tcp-local
protocol: TCP
- containerPort: 10055
name: metrics
protocol: TCP
- name: dnsmasq
image: docker.io/ist0ne/k8s-dns-dnsmasq-amd64:latest
livenessProbe:
httpGet:
path: /healthz-dnsmasq
port: 8080
scheme: HTTP
initialDelaySeconds: 60
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 5
args:
- --cache-size=1000
- --no-resolv
- --server=127.0.0.1#10053
#注释掉
#- --log-facility=-
ports:
- containerPort: 53
name: dns
protocol: UDP
- containerPort: 53
name: dns-tcp
protocol: TCP
# see: https://github.com/kubernetes/kubernetes/issues/29055 for details
resources:
requests:
cpu: 150m
memory: 10Mi
- name: dnsmasq-metrics
image: docker.io/ist0ne/dnsmasq-metrics-amd64:latest
livenessProbe:
httpGet:
path: /metrics
port: 10054
scheme: HTTP
initialDelaySeconds: 60
timeoutSeconds: 5
successThreshold: 1
failureThreshold: 5
args:
- --v=2
- --logtostderr
ports:
- containerPort: 10054
name: metrics
protocol: TCP
resources:
requests:
memory: 10Mi
- name: healthz
image: docker.io/ist0ne/exechealthz-amd64:latest
resources:
limits:
memory: 50Mi
requests:
cpu: 10m
# Note that this container shouldn't really need 50Mi of memory. The
# limits are set higher than expected pending investigation on #29688.
# The extra memory was stolen from the kubedns container to keep the
# net memory requested by the pod constant.
memory: 50Mi
args:
- --cmd=nslookup kubernetes.default.svc.huangzai.com 127.0.0.1 >/dev/null
- --url=/healthz-dnsmasq
- --cmd=nslookup kubernetes.default.svc.huangzai.com 127.0.0.1:10053 >/dev/null
- --url=/healthz-kubedns
- --port=8080
- --quiet
ports:
- containerPort: 8080
protocol: TCP
dnsPolicy: Default # Don't use cluster DNS.
2.创建并应用skydns-svc
[root@master dns]# cat skydns-svc.yaml
apiVersion: v1
kind: Service
metadata:
name: kube-dns
namespace: kube-system
labels:
k8s-app: kube-dns
kubernetes.io/cluster-service: "true"
kubernetes.io/name: "KubeDNS"
spec:
selector:
k8s-app: kube-dns
clusterIP: 10.254.0.100
ports:
- name: dns
port: 53
protocol: UDP
- name: dns-tcp
port: 53
protocol: TCP
三.修改节点kubelet的参数
1.在/etc/kubernetes/kubelet文件中增加一下内容
--cluster_dns=10.254.0.100 --cluster_domain=rorshach.com
增加完后如下所示
KUBELET_ADDRESS="--address=0.0.0.0 --cluster_dns=10.254.0.100 --cluster_domain=rorshach.com"
2.重启kubelet服务
systemctl restart kubelet
四.测试
[root@master ingress]# kubectl exec -it nginx-deployment-3606461909-s69n6 -- nslookup mysql-service nslookup: can't resolve '(null)': Name does not resolve Name: mysql-service Address 1: 18.211.9.206 ec2-18-211-9-206.compute-1.amazonaws.com
因为上文中的rorshach.com是实际存在的域名,所以我们在master上通过hosts指定该域名
[root@master k8s]# cat /etc/hosts 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 192.168.2.18 rorshach.com
再次测试:
[root@master k8s]# kubectl exec -it nginx-deployment-3606461909-s69n6 -- nslookup mysql-service nslookup: can't resolve '(null)': Name does not resolve Name: mysql-service Address 1: 10.254.12.207 mysql-service.default.svc.rorshach.com
已按预期呈现,现在我们就可以在应用程序中使用mysql-service这个服务名称来做host了